TC654 View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'TC654' PDF : 36 Pages View PDF
TC654/TC655
6.0 REGISTER SET
The TC654/TC655 devices contain 9 registers that pro-
vide a variety of data and functionality control to the
outside system. These registers are listed below in
Table 6-1. Of key importance is the command byte
information, which is needed in the read and write pro-
tocols in order to select the individual registers.
TABLE 6-1: COMMAND BYTE ASSIGNMENTS
Register
Command Read Write POR Default State
Function
RPM1
0000 0000
X
—
0 0000 0000 RPM Output 1
RPM2
FAN_FAULT1
FAN_FAULT2
0000 0001
X
0000 0010
X
0000 0011
X
—
0 0000 0000 RPM Output 2
X
0000 1010
Fan Fault 1 Threshold
X
0000 1010
Fan Fault 2 Threshold
CONFIG
STATUS
0000 0100
X
X
0000 0101
X
—
DUTY_CYCLE
0000 0110
X
X
MFR_ID
0000 0111
X
—
0000 1010
00X0 0X00
0000 0010
0101 0100
Configuration
Status. See Section 6.4 “Status
Register (Status)”, Status Register
explanation of X
Fan Speed Duty Cycle
Manufacturer Identification
VER_ID
0000 1000
X
—
0000 000X
Version Identification:
(X = ‘0’ TC654, X = ‘1’ TC655)
6.1 RPM-OUTPUT1 & RPM-OUTPUT2
Registers (RPM1 & RPM2)
As discussed in Section 4.7 “Sensing Fan Operation
(SENSE1 & SENSE2)”, fan current pulses are detected
at the SENSE1 and SENSE2 inputs of the TC654/
TC655 device. The current pulse information is used to
calculate the fan RPM. The fan RPM data for fans 1 and
2 is then written to registers RPM1 and RPM2, respec-
tively. RPM1 and RPM2 are 9-bit registers that provide
the RPM information in 50 RPM (8-bit) or 25 RPM (9-
bit) increments. This is selected via RES (bit 6<0>) in
the Configuration Register, with ‘0’ = 50 RPM and
‘1’ = 25 RPM. The default state is zero (50 RPM). The
maximum fan RPM value that can be read is
12775 RPM. If this value is exceeded, R2CO (bit 4<0>)
and R1CO (bit 3<0>) in the Status Register will be set to
a '1' to indicate that a counter overflow of the respective
RPM register has occurred. Register 6-1 shows the
RPM output register 9-bit format.
REGISTER 6-1: RPM OUTPUT REGISTERS (RPM1 & RPM2)
D(8)
D(7)
D(6)
D(5)
D(4)
D(3)
D(2)
D(1)
D(0)
RPM
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
25
0
0
0
0
0
0
0
1
0
50
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
1
1
1
1
1
0
12750
1
1
1
1
1
1
1
1
1
12775
2002-2014 Microchip Technology Inc.
DS20001734C-page 17
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